The proposed demonstration study will help build the evidence of potentially sustainable and disseminable intervention strategies to prevent and control childhood obesity. This study, conducted by the Institute for Behavioral & Community Health in conjunction with the Imperial County Public Health Department and the Federally Qualified Health Center, Clinicas de Salud del Pueblo, Inc., will evaluate a multi-sector, multi-level intervention to address childhood obesity in Imperial County, the county in the State of California with the highest rates of childhood obesity (39% vs. 28% statewide). In coordination with the Centers for Disease Control and Prevention (CDC), the Evaluation Center, and the other funded sites, this study will occur in three phases. Phase 1 (Year 1) will consist of formative research to refine the intervention and evaluation protocols. Methods will include audits, focus groups, in-depth interviews, and archival research. Regular meetings with proposed partners and with the other funded sites, the Evaluation Center and CDC will occur during this phase to determine measurement at all levels of influence. Phase 2 (Year 2 through Year 4, Month 3) will assess the impact of the multi-sector, multi-level intervention on the health of 1440 children between 2 and 10 years old. Two clinics will be assigned to a multi-sector, multi-level intervention (MSML) and one clinic will be assigned to a health care system (HCS) intervention. Consistent with funder requirements, this demonstration study will use evidenced-based strategies to target a consistent set of behaviors to promote a healthy diet, physical activity, and fewer sedentary behaviors in four different sectors: federally qualified community health centers, childcare centers, elementary schools, and the community (restaurants and parks & recreation departments). As an added innovation, the proposed project will also target the family system and the home environment, which will be linked with the health care system intervention through a promotor program. All intervention activities will target multiple levels of influence including policy, systems, and the environment. Phase 3 (Yr 4, Months 4-12) will involve evaluating the efficacy and cost-effectiveness of the intervention, preparing for sustainability and dissemination, and preparing products such as manuscripts, reports, and usability manuals. The intervention goal is to develop a childhood obesity chronic care model that recognizes the communities' assets and needs. The evaluation goal is to assess the efficacy of the intervention on the body mass index (BMI) z-score of 1440 children over a two-year period. The process evaluation examines nearly all dimensions important for informing the potential to sustain and disseminate intervention components to similar rural and low-income communities. Finally, cost-effectiveness analyses will examine change in BMI z-score, with dollars per change in BMI z-score being the primary ratio evaluated. It is hypothesized that MSML children (n=720) will experience greater reductions in their BMI z-score than HCS children (n=720) at the 12- month post-baseline follow-up and sustain these changes at the 24-month follow-up.